Measuring instrument



3 1938- w. BERNDT ET AL 2,128,395

MEASURING fNSTRUMENT Filed May 19, 19157 RADIO RECEIVER INVENTORS W BERNDTAND H. E. PAUL ATTO'RNEY Patented Aug. 30, 1938 UNITED STATES PATENT OFFICE 2,128,395 MEASURING INSTRUMENT Walter Berndtand Hans Erich Paul, Berlin, Germany, assigns to Telefunken Gesellschaft iiir Drahtlose Telegraphic m. b. 11., Berlin, Germany, a corporation of Germany Application May 19, 1937, Serial No. 143,491

Germany Claims.

ments known in the art. 3 Another arrangement designed to measure the output potential of receivers is known in the prior potentials of glow-tubes, it connected in proper circuits, are quite well defined, though the luminous efl'ect is poor. But the greater the requisite brilliance or luminosity of the glow-tube, the re- July 6, 193 (CI. 179 175.31) For measuring or comparing the output potenin a dark room. Hence, accuracy of the measure ments is greatly dependent upon the illumination of the ambient.

present, and this simply on the ground that optical indication is relied upon.

Far more favorable is acoustic indication as 10 for instance, of a potentiometer such a high negaure and criterion for the value of the output potential of the receiver.

But this scheme involves the shortcoming that suddenly, but decreases very gradually. However,

device a biased glow-discharge path or a con- 0 this pathrepresents no essential resistance for ,35

matching is insured between the various inner 40 A circuit organization without transformers is veloped across iron-cored coil D and transferred through condenser C. The measurement takes place in the following manner: By reduction 01' the biasing voltage at fering stations which come in with a higher poconnections between said glow tube electrodes and tential will, to be sure, then still be audible, but spaced apart points on saidresistor.

can aurally be distinguished from the signal to 2. The method of measuring an alternating be measured. The more the biasing voltage may current of audio frequency which comprises the 5 be diminished, the higher the output potential steps of transmitting the current through the of the receiver. Adjustment of the potentiometer space between the electrodes of a glow discharge furnishing thebiasing voltage may be provided tube, converting the transmitted current into with a scale calibrated to read directly in terms sound waves and applying a steady potential beof receiver output potential. But it will be found tween said electrodes of such value that the total desirable to furnish the' calibrated scale with efiective voltage therebetween isjust suflicient to variable zero (null) point adjustment. cause the sound waves to be audible.

The arrangement of the invention particularly 3. A measuring device comprising the combinamakes it feasible to compare receiver output potion of an amplifying tube having an anode, an tentials subject to variations with time with a input transformer having its primary connected 5 constant output potential from an auxiliary or to said anode, an output transformer having primeasuring oscillator. This is the principle unmary and secondary windings, a glow discharge derlying most outfits designed to measure the tube having one electrode connected to one end v field intensity of transmitter stations. The preof the secondary winding of said input transformcision of the measurements, when using a calier and its other electrode connected to one end of 0 brated adjustable auxiliary transmitter or oscilthe primary of said output transformer, a circuit lator, is independent of the calibration of the including a condenser connectingthe other end of potentiometer furnishing the biasing voltage since the secondary of] said input transformer to the it sufiices to work at constant potentiometer adother end of the primary of said output transjustment without knowing the absolute values of former, means for applying a variable unidirecthe receiver output potential. V tional potential between the electrodes of said One special advantage residing in the use of glow discharge tube and a sound translating dea glow-discharge path is that the discharge path vice coupled to the secondary winding of said requires no additional circuit elements such as a output transformer. triode tube and that there is no need for a heat- 4. An indicating device comprising the combiing source. Hence, in order to measure the outnation of an amplifying tube having an anode,

put potential of a receiver apparatus, all that is an inductance coil having its high potential end required is a potentiometer and a small glowconnected to said anode, a source of positive podischarge path, for the rest of the equipment is tential connected to the low potential end of already in the receiver itself. Moreover, the glowsaid inductance, a glow discharge path and a discharge path requires but little space so that it sound translating device connected in series bemay be mounted at any desired place in the intetween the high potential end of said coil' and rior oi the receiver case; hence, the entire measthe negative terminal of said potential source. uring outfit may be fitted in any receiver after it 5. An indicating device comprising the combihas been completed, a feature that has been unatnation of an amplifying tube having an anode, 40 tainable in arrangements known in the prior art an inductance coil having its high potential end on account of lack of space. The arrangement connected to said anode, a source of steady pohereinbefore described may be used not only in tential having its positive terminal connected to connection with receivers, but also with amplifiers the low potential end of said coil, a series circuit of any kind. comprising a condenser, a glow discharge tube Having described our invention, what we claim and a sound translating device arranged in the and desire to-secure by Letters Patent is: order named connected between said anode and 1. A measuring device comprising the combithe negative terminal of said potential source, a nation of an amplifying tube having an output resistor connected across the terminals of said circuit, a sound translating deviee,-a circuit coupotential source and a connection between an inpling said output circuit and translating device termediate point of said resistor and one electrodt and including a series connected glow discharge of said glow'discharge tube. tube having two electrodes, a steady source of potential, a resistor connected across the termi- WALTER BERNDT. nals of said potential source and direct current HANS ERICH PAUL. 

